The present invention relates generally to agricultural implements and, more particularly, to an opener that provides double-shoot, single pass deposition of fertilizer and seed onto a planting surface with horizontal and/or vertical stratification.
Fertilizer and seed are generally deposited onto a planting surface in either a single shoot or double shoot manner. With a single shoot planting technique, a mixture of seed and fertilizer is deposited into a single furrow and subsequently packed. With a double shoot planting technique, seed and fertilizer are deposited into separate furrows, which may or may not be closely spaced, and then packed.
A single shoot planting device or opener typically has a single delivery hose through which the mixture of granular fertilizer and seed is delivered to the furrow. More particularly, a single shoot planting device will typically include a cutting tip that is dragged at a depth just below the planting surface. The delivery hose extends along a backside of the cutting tip, or knife, so that the fertilizer and seed mixture is deposited into the furrow immediately after the cutting tip cuts into the planting surface. Ideally, the mixture is deposited in to the furrow before the furrow collapses. The furrow is typically packed by a trailing packing or press wheel.
Another configuration of a single shoot planting device replaces the knife with a disc or coulter that rotates at an angle relative to a line of travel to form a furrow or trench in the planting surface. Because of the angling of the disc, the leading face of the disc pushes soil to one side and creates the furrow while the opposite, trailing face of the disc runs in the “shadow” of the leading face. The seed/fertilizer mixture is dropped to the bottom of the furrow while the furrow is held open by the disc and a cooperating plate (or scraper or seed boot) on the other side. The penetration depth of the disc controls the seed depth. A trailing packer wheel closes the furrow after the mixture is deposited and firms the planting surface (soil).
While single shoot planting units are less complex, it is generally preferred to use a double shoot planting unit which allows seed and fertilizer to be separately deposited into the furrow. When the fertilizer and seed are mixed, reduced concentrations of fertilizer must be used to prevent the seed from becoming damaged, i.e., “burnt”. In one exemplary double shoot planting unit, a knife has a side tip (side bander) that trails the leading knife as the planting unit is towed along the planting surface. The knife creates a furrow or fertilizer trench and the side bander forms a ledge in the sidewall of the furrow to effectively form a seed trench or seed bed. The fertilizer and seed trenches are separated from one another both horizontally and vertically. This separation provides a fertilizer/seed stratification that has been found to provide better growing conditions, i.e., higher concentrations of fertilizer may be used without seed “burning”.
In yet another type of double shoot planting unit, a pair of rotating discs are used to form separate fertilizer and seed trenches having horizontal and vertical stratification. The leading disc cuts through the planting surface at an angle to cut a furrow or fertilizer trench. A trailing disc cuts through the side of the furrow formed by the leading disc to cut a seed trench that is generally horizontally and vertical offset from the fertilizer trench. U.S. Pat. No. 5,752,454 describes a dual disc, double shoot planting unit.
Dual disc units, such as that described in U.S. Pat. No. 5,752,454, are relatively complex structures with multiple rotating parts such as the discs themselves and associated bearings. This complexity also adds to the overall cost of the planting unit and the implement. Dual disc units, such as those described in the aforementioned patent, have also been found to perform unsatisfactorily in soft soil conditions. More particularly, the discs are generally angled to essentially “dig” into the soil surface to cut a furrow. Since the discs dig into the surface, less down pressure is needed. In harder soil conditions, the disc will effectively dig into the soil as the soil itself provides bias against which the disc can leverage. However, in soft soil conditions, the disc will essentially “plow” through the soil rather than cut an open furrow. Furthermore, to accommodate the space needed for two rotational elements, the distance between the leading and trailing discs is relatively substantial and can led to disturbance of the furrow before the seed is planted. In other words, depending upon soil conditions, the furrow may collapse upon itself before the trailing disc cuts a seed bed into the furrow formed by the leading disc. The spacing between the discs also adds to the overall size, weight, and cost of the carrying frame.